Test Bench for Web: B&W XT Series Home Theater Speaker System
Frequency response (at 2 meters) front left/right: 41 Hz to 20 kHz ±4.7 dB center: 71 Hz to 18.3 kHz ±4.3 dB surround: 76 Hz to 15.3 kHz ±3.8 dB subwoofer: 35 Hz to 104 Hz ±1.9 dB
Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input) front left/right: 85 dB center: 86 dB surround: 84 dB Impedance (minimum/nominal) front left/right: 3.5/14 ohms center: 4.5/11 ohms surround: 5.5/13ohms
Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters in a large room) front left/right: 40 Hz at 83 dB center: 62 Hz at 70 dB surround: 62 Hz at 70 dB subwoofer: 32 Hz at 76 dB SPL 96 dB average SPL from 32 to 62 Hz 104.9 dB maximum SPL at 62 Hz bandwidth uniformity 91%
All the curves in the frequency-response graph are weighted to reflect how sound arrives at a listener's ears with normal speaker placement. The curve for the left/right front channels reflects the XT4's response with the speaker standing on the floor, averaged over a ±30° window with double weight at 30° (the most typical listening angle). The center-channel curve reflects the XTC's response averaged over ±45°, with double weight directly on-axis of the primary listener. The surround-channel curve shows the XT2's response averaged over ±60°. Both the XTC and XT2 were placed on a 6-foot stand for measurement, which gives anechoic results to approximately 200 Hz. Except for the subwoofer, all measurements were taken at a full 2 meters, which emulates a typical listening distance, allows the outputs of large speakers to fully integrate acoustically and, unlike near-field measurements, includes front-panel reflections and cabinet diffraction.
TOWERS/SATELLITES The bass-reflex XT4 tower has excellent low-frequency extension for system with such a slender cabinet and small drivers. There is a relatively small (compared to other floorstanding speakers) floor reflection-dip centered at 240 Hz, followed by an octave-wide depression centered at 2 kHz and gently falling response above 8 kHz. Directivity, or off-axis response, is essentially identical at any listening angle inside our ±30° listening window. Plugging one port cuts lower bass below 49 Hz, while plugging both ports raises the fall-off point to 51 Hz.
The XT2 bookshelf speaker's response has a similar characteristic but without the floor-bounce notch and extended low-frequency output that come as a function of the XT4's woofer section and floorstanding design. Directivity is quite uniform, with only a high-frequency falloff at wide listening angles. Consequently, when the XT2 is used as a surround speaker, surround-channel information will arrive at listeners' ears with timbre similar to that of the left/right channels.
On the other hand, although the XTC center channel uses the same drivers, their symmetrical horizontal array produces off-axis lobing that begins at ±15° off-axis and worsens as the microphone is moved further away from the center of the listening window. By the time it reaches a position 45° off-axis from the ideal listening position, the response has a 25-dB notch at 1.2 kHz. The XT4, XT2, and XTC all have relatively low sensitivity and may need reasonably powerful amplifiers to reach satisfactory loudness with dynamic program material.
SUBWOOFER The PV1 subwoofer's bass limits were measured with it set to maximum bandwidth and placed in the optimal corner of a 7,500-cubic-foot room. In a smaller room users can expect 2 to 3 Hz deeper extension and as much as 3 dB greater sound-pressure level (SPL).
B&W says the PV1's balanced twin-radiator design yields an essentially motionless cabinet, even when played at loud listening levels. On the other hand, like other mini-cabinet subwoofers we've tested, it has both limited upper and lower bass extension and dynamic capability that falls off at nearly 18 dB per octave below 62 Hz. All primary measurements were made with the PV1 in EQ1 mode. Switching to EQ2 begins limiting bass at 50 Hz with a -3 dB ultimate reduction. EQ3 begins limiting bass at 100 Hz with a -8 dB reduction at the lowest frequencies. On the sample I tested, the crossover control had no action, so the unit was probably damaged at some point in testing or shipping.